Rootstock refers to the part of a plant, typically the root system, onto which another plant variety is grafted. This technique is commonly used in horticulture to improve disease resistance, enhance growth, or adapt plants to different soil conditions. The rootstock provides the necessary nutrients and stability for the grafted plant, which is often referred to as the scion. In viticulture, for example, grapevines are often grafted onto specific rootstocks to combat pests like phylloxera and to improve the overall health of the vine. Different rootstocks can influence the flavor, yield, and vigor of the resulting plant, making the choice of rootstock crucial for successful cultivation.